1. Field of the Invention
This invention concerns a shaker or picking arm with adjustable stiffness for harvesting machines, especially for grape harvesting machines, of the type comprising two berry detaching assemblies placed facing each other and each comprising a plurality of superimposed shakers or picking arms. The invention applies also to harvesting machines and especially to grape harvesting machines of the above-mentioned type using such shakers. It also concerns a disengaging device permitting to neutralize one or more shaker(s) on each of both assemblies of the machine shaking head.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
The world of viticulture is today constantly looking for solutions to improve the various harvesting systems of grape harvesters.
For a few decades, many solutions have been proposed to the wine growers who use mechanical grape harvesting, or to those who used to harvest by hand and became mechanized based on the harvesting quality level achieved with modern grape harvesters.
However, the quality of the grape harvest achieved still remains highly random and depends on several parameters, including human assessment parameters and mechanical performance parameters of the systems that make up the harvesting head of such harvesting machines.
With regard to human parameters, much progress has been made in the ergonomics of the controls for adjustment of the harvesting part of grape harvesters. For the harvesting head adjusting part, three main separate assemblies can be considered: The vine shaking part, the harvest conveying part and the harvest cleaning part. The ergonomic access to the various adjustments of a vine harvester harvesting head enable the vine growers to apprehend much more quickly the adjustments so as to obtain the best quality results for the harvest.
With regard to the mechanical performance parameters, many improvements have been made on the three parts described above, and more specifically on the vine shaking systems.
The vine shaking system is by far the most important part of a grape harvester harvesting head.
It is indeed easy to understand that on a harvesting head, one part of the system is designed to correct any insufficient quality generated by the other systems. For example, the vine cleaning system must be better performing, if the shaking system is under performing, since it generates a lot of leaves and plant debris of all kinds that are to be eliminated.
Several shaking systems for harvesting machines such as grape harvesters are presently known.
The eldest and simplest of these systems uses threshers consisting of simple flexible rods made out of fiberglass and attached at one of their ends onto a shaking arm activated angularly and alternatively by a mechanical crank-rod (see for example FR-2.509.955, FR-2.554.673, FR-2.437.769).
The advantages of this almost completely abandoned system were to be very simple and to be slightly adjustable. Indeed, if one wanted to adjust the fitting, it was possible, but the counterpart was that the amplitude at the end of the thresher decreased significantly, which was not really acceptable as it reduced greatly the travel speed performance of the harvesting machine inside the vine and therefore was of no use.
Furthermore, the very big disadvantage of this thresher system with attachment at only one end of the “threshing” rod was the application to the vegetation of whipping type blows, known as racing phenomenon in the concerned professional environments.
This racing phenomenon results from the relation existing between the thresher stiffness and its specific inertia, leading to a more or less high natural operating frequency that must be, if possible, the farthest from the shaking operating frequencies, and preferably much higher. That was not the case for this type of thresher.
This frequency usually ranges from 450 to 600 strokes per minutes, or from 7.5 to 10 Hz.
Because of its many disadvantages, this system is no longer used today on modern grape harvesters.
At the present time, the most common shaking system uses “shakers” (for example, FR-2.638.602, FR-2.768.016). Such system operates according to the same principles as the previous one, except that it is activated using two shaking arms on each side, with the whole unit having the same type of mechanical crank-rod drive system. The main difference existing between the shaker and the thresher is that the thresher is attached at only one end and that the shaker is attached at both ends because of its general shape as a trombone. This trombone shape gives it an advantage over the older threshing system.
The double attachment indeed enables the system to move while generating a racing phenomenon much less harmful that the one produced by the above-described threshing system.
The stiffness and inertia ratio is indeed much more favorable that the one obtained with the thresher system, which permits to control it better and thus to have a greater adjustment capability, especially with regard to frequency. It is easy to understand that the higher the frequency, the more rigid the shaker must be in order to have a natural frequency higher than the service frequency. Being able to increase the shaking frequencies makes it possible for the grape harvesters equipped with a shaker harvesting system to move much faster than the grape harvesters equipped with a thresher harvesting system.
On some grape harvesters, the shaker systems can be slightly adjustable just like the above-described thresher systems. It is indeed possible, just like on the threshers, to attach both ends of the shaker in a fixing position more or less far from the rotation axis of the shaking shaft so as to modify the bending stiffness. This being said, just like for the threshers, this adjustment has the adverse effect of modifying their amplitude and thus to significantly slow down the machine harvesting speed. This is why many users, even maybe all of them, do not use at all this adjustment capability as it is too difficult to evaluate and to control.
The shaker harvesting system is today conventional and one of the most commonly used on modern grape harvesters.
Another complex shaking system is for example described in FR-2 605 487, FR-2 789 262 and FR-2 813 493 documents.
The shaking system described in these documents comprises shakers consisting of arc-shaped flexible rods whose two ends are connected to a support. A means permits to modify the curvature of these rods.
To that effect, one of the ends of each flexible rod is attached through an articulation to a fixed component of the machine while the opposite end is attached at a mobile point in a direction parallel to the longitudinal axis of the machine through connecting rods or another articulated transmission system.
Such a system is close to a thresher type shaking system, except that at the rear end of the shakers a pivot attachment is provided with a connecting link to support the forward and backward residual movement. The advantage of this rear connecting link attachment is to eliminate the racing disadvantages mentioned above in the thresher type shaking systems. On the other hand, the disadvantage of this system is its great complexity and the fact that it causes the shaker to work under permanent deformation. This permanent deformation makes it necessary to have a very high strength shaker and thus with a greater section than a conventional shaker. Having a shaker with a greater section causes greater inertia in movement. This is why this type of shaking is usually suspended in a pendular manner in the harvesting head.
The disadvantage of this system is that it requires the use of a very large number of mechanical parts, which makes the removal of the shakers more painstaking than on a conventional system.
It is mainly because of the complexity of removal and reinstallation of the shakers that a locking and unlocking system of said shakers was proposed in order to avoid their removal when the number of shakers assembled is greater than necessary based on the height of the fruit-bearing area to be harvested (FR-2 813 493). This locking and unlocking system complicates even further the attachment of the shakers, which does not favor mechanical simplification and smaller inertia of the moving parts, which is the enemy of vibratory systems.
The advantage of the system described in FR-2 605 487, FR-2 789 262 and FR-2 813 493 documents is its power. Because of the number of moving parts and its great inertia, the system has indeed a large kinetic energy reserve, which is an advantage when one wants to move fast and hit hard, especially when the vines are difficult. On the other hand, when the vines are delicate, this advantage becomes a major inconvenient because of the great stiffness of the shakers.
Finally, a shaking device for grape harvesters comprising a plurality of shakers is known. Each one of these shakers consists of a flexible rod folded onto itself by approx. 180° by having the shape of a hairpin, with both branches of the rod having practically the same length, with the end of one of the branches of this rod connected to a drive shaft while the end of the other branch of said rod is connected either to a fixed element of the machine frame (FR-2.639.177), or with a moving capability (FR-2.651.408 and FR-2.668.025) to a support device.
The branch of the shakers that is turned toward the vegetation whenever said shakers are installed in the tunnel of a grape harvester harvesting head, i.e., the branch connected to the drive shaft, is wrapped in a protective sleeve made out of a soft material (FR-2.639.177 and FR-2.651.408).
This soft protective sleeve permits to mitigate the harmful effects generated by the shocks of said shakers onto the fruit and vegetation of the fruit hedges when harvesting. On the other hand, it does not have any impact on the degree of stiffness or flexibility of the shaking rod that remains the same, regardless of whether said shaking rod is coated or not with a soft protective sheath. The soft protective sheath surrounding the shaking rod does not permit to adjust the degree of flexibility or stiffness of this rod. Furthermore, it is mounted in a fixed manner on the shaking rod along which it cannot be moved based on the characteristics of the vines to be processed (vegetation, vine variety, degree de maturity.)